Lecture
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Play gamestr.length , str.toUpperCase() num.toFixed All values in JavaScript, with the exception of null and undefined , contain a set of auxiliary functions and values accessible "through the dot".
Such functions are called "methods", and values - "properties". Let's look at examples.
str.length , str.toUpperCase() The string has a length property that contains a length:
1 | alert( "Привет, мир!" .length ); // 12 |
Strings also have a toUpperCase() method that returns an uppercase string:
1 | var hello = "Привет, мир!" ; |
2 |
3 | alert( hello.toUpperCase() ); // "ПРИВЕТ, МИР!" |
If a function is called through a point ( toUpperCase() ), this is called a “method call” if you simply read the value ( length ) - “property retrieval”.
num.toFixed Numbers have a num.toFixed(n) method. It rounds the number num to n decimal places, if necessary, finishes with zeros to a given length and returns as a string (conveniently for formatted output):
1 | var n = 12.345; |
2 |
3 | alert( n.toFixed(2) ); // "12.35" |
4 | alert( n.toFixed(0) ); // "12" |
5 | alert( n.toFixed(5) ); // "12.34500" |
The details of the toFixed work are toFixed in the Numbers chapter
The number method can also be addressed directly:
1 | alert( 12.34.toFixed(1) ); // 12.3 |
... But if the number is an integer, then there will be a problem:
1 | alert( 12.toFixed(1) ); // ошибка! |
This is a feature of JavaScript syntax. This is how it will work:
1 | alert( 12..toFixed(1) ); // 12.0 |
Pay attention, for the method call after its name there are brackets: hello.toUpperCase() . Without brackets the method will not be called.
Let's see, for example, the result of a call to toUpperCase without brackets:
1 | var hello = "Привет" ; |
2 |
3 | alert( hello.toUpperCase ); // function... |
This code displays the value of the toUpperCase property, which is a function embedded in the language. Typically, the browser displays it something like this: "function toUpperCase() { [native code] }" .
To get the result, this function must be called, and just for this in JavaScript brackets are required:
1 | var hello = "Привет" ; |
2 |
3 | alert( hello.toUpperCase() ); // "ПРИВЕТ" (результат вызова) |
We will meet with lines and numbers in later chapters and learn more about the means to work with them.
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Scripting client side JavaScript, jqvery, BackBone
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